XEP-0073: Basic IM Protocol Suite

Abstract:

This document defines a recommended suite of Jabber/XMPP protocols to be supported by basic instant messaging and presence applications. Note: This protocol suite has been obsoleted by XEP-0211 and XEP-0212.

WARNING: This document has been obsoleted by the XMPP Standards Foundation. Implementation of the protocol described herein is not recommended. Developers desiring similar functionality are advised to implement the protocol that supersedes this on
(XEP-0242, XEP-0243).

Given the large number of Jabber/XMPP protocols,
[3]
it is not always clear to developers exactly which protocols they need to implement in order to interoperate over Jabber/XMPP networks. This document attempts to assist developers by defining a protocol suite for basic instant messaging and presence.

Defining a protocol suite provides a high-level "bucket" into which we can place specific functionality areas for development and compliance testing. A baseline is provided by RFCs 3920 and 3921, which define XML streams, JID processing, channel encryption, authentication, the three primary XML stanza types (<message/>, <presence/>, and <iq/>), namespace handling, presence subscriptions, roster management, and privacy lists (whitelisting/blacklisting). However, basic Jabber instant messaging and presence applications should support several additional protocols that were not included in the XMPP specifications for either of the following reasons:

They were not required to meet the requirements of RFC 2779 [12] (e.g, service discovery)

They were and remain in common use within the Jabber community but did not meet the more stringent requirements of the IETF (e.g., old-style, non-SASL authentication)

The software developed in the Jabber community is built on the foundation of XML streams, a consistent addressing scheme (JIDs), channel encryption, authentication of an entity (client or server) with a server, three core data elements (<message/>, <presence/>, and <iq/>), and proper handling of XML namespaces. These foundational building blocks have been formalized within RFC 3920, support for which is REQUIRED by this protocol suite.

However, XMPP Core is not fully congruent with the core of what has traditionally been known as "Jabber", and this divergence needs to be captured in the Basic IM Protocol Suite. For the sake of backward compatibility, support for Non-SASL Authentication (XEP-0078) [14] is RECOMMENDED for servers (but not clients) as a fallback method of authentication by older deployed clients. [15] In addition, support for the error 'code' attribute specified in Error Condition Mappings (XEP-0086) [16] is RECOMMENDED for both clients and servers.

RFC 3920 does not define everything that is normally expected of even a minimal instant messaging and presence application (in effect, it defines the transport layer rather than the IM and presence application layer). Much of this IM and presence functionality is defined in RFC 3921 in order to meet the requirements of RFC 2779. In particular, RFC 3921 defines roster management, presence subscriptions, and routing and delivery guidelines for clients and servers. Therefore, support for RFC 3921 is REQUIRED.

Furthermore, Jabber instant messaging and presence applications typically include the ability to discover information about other entities on the network, and to reply to queries for information. This behavior is extremely helpful because it ensures that entities on the network can determine each other's capabilities and thus understand how to communicate together. Therefore, support for Service Discovery (XEP-0030) [17] is REQUIRED by this protocol suite, as is (for clients) the dynamic profile of service discovery specified in Entity Capabilities (XEP-0115) [18].

Traditionally, Jabber servers (and some services) have also offered the ability for clients to register accounts "in-band" (see In-Band Registration (XEP-0077) [19]) in order to bootstrap participation on the network; support for that protocol is RECOMMENDED but any given server deployment MAY disable in-band registration as a matter of service provisioning.

RFC 3920 requires support for SASL and TLS as must-implement protocols, and that support is not modified herein. The older authentication method specified in XEP-0078: Non-SASL Authentication is now deprecated; however, support for it is still recommended in server implementations for the sake of backward compatibility (see XEP-0078 regarding the proper order of precedence between SASL authentication and non-SASL authentication).

Appendix C: Legal Notices

Copyright

Permissions

Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation.

Disclaimer of Warranty

## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. ##

Limitation of Liability

In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages.

IPR Conformance

This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which can be found at <https://xmpp.org/about/xsf/ipr-policy> or obtained by writing to XMPP Standards Foundation, P.O. Box 787, Parker, CO 80134 USA).

Appendix D: Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 6120) and XMPP IM (RFC 6121) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.

Appendix E: Discussion Venue

The primary venue for discussion of XMPP Extension Protocols is the <standards@xmpp.org> discussion list.

Appendix F: Requirements Conformance

The following requirements keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".

Appendix G: Notes

3. The protocols developed by the Jabber community have matured considerably since 1999. The core protocols were originally created by a small group of developers who worked on early Jabber-related open-source software projects such as the jabberd [4] server, the Winjab, Gabber, and Jarl clients, the Net::Jabber and Jabberbeans libraries, and gateways to consumer IM services. In the summer of 2001, the XMPP Standards Foundation (XSF) [5] was founded to institute a formal standards process within the growing Jabber community (codified in XMPP Extension Protocols (XEP-0001) [6]). In late 2002, the Internet Engineering Task Force (IETF) [7] formed the XMPP Working Group [8], which formalized the core Jabber protocols under the name Extensible Messaging and Presence Protocol (XMPP). In early 2004, the IETF approved the main XMPP specifications as Proposed Standards within the Internet Standards Process defined by RFC 2026 [9], resulting in publication of RFC 3920 [10] and RFC 3921 [11]. In the meantime, the XSF has continued to develop additional protocols on top of XMPP in order to address functionality areas that are too application-specific for consideration within the IETF.

4. The jabberd server is the original server implementation of the Jabber/XMPP protocols, first developed by Jeremie Miller, inventor of Jabber. For further information, see <http://jabberd.org/>.

5. The XMPP Standards Foundation (XSF) is an independent, non-profit membership organization that develops open extensions to the IETF's Extensible Messaging and Presence Protocol (XMPP). For further information, see <https://xmpp.org/about/xmpp-standards-foundation>.

7. The Internet Engineering Task Force is the principal body engaged in the development of new Internet standard specifications, best known for its work on standards such as HTTP and SMTP. For further information, see <http://www.ietf.org/>.

8. The XMPP Working Group was created by the Internet Engineering Task Force to define an adaptation of the base Jabber protocols that could be considered an IETF-approved instant messaging and presence technology. For further information, see <https://datatracker.ietf.org/wg/xmpp/charter/>.

15. Older software also used port 5223 for SSL-enabled communications between a client and a server, rather than upgrading port 5222 as is done during TLS negotiation (the equivalent for server-to-server communications was never implemented). Support for this behavior is OPTIONAL on the part of servers for backwards-compatibility with older deployed clients.

20. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.

21. The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <https://xmpp.org/registrar/>.

Appendix H: Revision History

Version 1.2 (2007-10-30)

Per a vote of the XMPP Council, changed status to Obsolete and referred implementors to XEP-0211 and XEP-0212.

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Version 1.1 (2007-02-15)

Changed support for XEP-0077 from required for servers and recommended for clients to recommended for both servers and clients; changed support for XEP-0078 from required for both servers and clients to recommended for servers and not recommended for clients; changed support for XEP-0086 from required for servers and recommended for clients to recommended for both servers and clients; added XEP-0115 as required for clients.

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Version 1.0 (2004-12-09)

Per a vote of the Jabber Council, advanced status to Active.

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Version 0.10 (2004-12-06)

Per feedback from the Jabber Council, made all of RFC 3920 mandatory (no loophole allowing certain client platforms to not support TLS and SASL).

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Version 0.9 (2004-12-01)

Removed reference to deployments and moved historical paragraph to a footnote.